Electrical resistance alloys



United tates atent ELECTRICAL RESISTANCE ALLOYS 2,850,383 Patented Sept. 2, 1958 "ice can be achieved by the provision and utilization of alloy 5 compositions consisting essentially of from 2 to 4.5% Carrol Dean Starr, Whippany, and James E. Daly, of Al, 1 to 7% of V, .1 to 10% of Mo and to 25% Colonia, N. 1., assignors to Wilbur B. Driver Comof Cr in a nickel base, when the total content of Cr and P y, Newark, B c6l'pol'afioil of New Jersey M0 in the alloys does not exceed 30%.

N 0 Drawing Application September 26 1956 10 NiC r type alloys of this formulation possess valuable $3521 612,107 properties of corrosion resistance, strength and ductility s1m1lar to those of known electrical res1stance alloys or 5 Claimsthe NiCr type. Being both hot workable and cold workable, they can be readily converted from ingot form into the form of fine resistance elements, such as wires,

This invention relates to electrical resistance alloys of 15 ribbons or other pliable strands. We have further disthe nickel-chromium type and to resistance elements made covered, however, that when these alloys are suitably of these alloys, which are particularly suitable for use in annealed and heat-treated, the products obtained have electrical or electronic control devices. "an extraordinarily high resistivity of at least 950 ohms Nickel-chromium electrical resistance alloys are comper circular mil foot, and their temperature coefiicient or" monly made with a base composed of Ni and from 10 resistance is so small that it departs from zero, if at all, to 30% of Cr. The resistivity and the temperature coby not more than about .000020 ohm per ohm per deeflicient (T. C.) of products made of these alloys, such gree C. over the temperature range of 20 to 100 C. as wires or ribbons or other pliable strands, are properties Illustrative examples of the alloys and resistance eleof great importance to the usefulness of the products in ments of this invention are set forth in Table I hereof. electrical or electronic control devices, such as resistors, As to each example, this table shows the Weight percentpotentiometers and the like. age of the essential alloy ingredients, as determined by A typical alloy of 80% Ni and 20% Cr, when drawn chemical analyses, the important resistance properties of into fine wire and subsequently strand annealed, shows heat treated .0253" wire strands made of the alloy, and a resistivity of approximately 612 ohms per circular mil the conditions of heat treatment. The strands had been foot (c. m. f.) and a temperature coefiicient of resistance annealed at 1750 F. to 2150" F. in a 12 foot furnace of about .00018 ohm per ohm per degree Centigrade over at a speed of 42 ft./rnin., cooled rapidly and then heat the temperature range of 20 to 100 C. When suitably treated in a reducing atmosphere of cracked ammonia at heat treated, its resistivity rises to about 650 ohms/c. 1n. f., the temperatures and for the times listed in Table l. and its temperature coefilcient is reduced to about .00009 All th alloys conta ned as incidental elements very ohm/ohm/ C. small amounts of C, Ca, Co, Fe, Mg, Pb, Si and Zr.

It is known that the resistivity of such allgys may b When the aluminum content of compositions like those substantially increased by adding to a nickel-chromium 0 th going examples is increased above 4.5%, the base suitable amounts of certain alloying l me t partiresistivity of heat treated strands of the alloys still reaches cularly Si, Mn and Fe, V and Fe, Mn, V and Fe, Cu approximately 1000 ohms/c. m. f., but there is an inorand Al, or Cu, Al and Fe. When suitably fabricated, dinate increase of the temperature coefiicient which strand annealed and heat treated, some of the resulting m k he pr s unsui le for the requirements of compositions show a very low temperature coefficient hat fine electrical resistance elements. When the vanadium varies from zero by not more than about .000020 ohm Content is increased ab0v6 30% or the mfilybdamlm per ohm per degree C. content is increased above 10%, the compositions no As far as We are aware, however, there is no known longer have the desired ductility and working properties. composition of a Ni-Cr type alloy that can be processed When the aluminum content is reduced below 2%, the commercially into electrical resistance elements having required high resistivity is not attained.

Table 1 Strand Heat Time Heat treated strands Per- Per- Per- Per- Peranneal treat of Example cent cent cent cent cent temp, temp., heat Al Mo Cr Ni F. F. treat, Resistivity T. 0., Q/S2/ C.

hours S2/C.M.F. (20- 0 C.)

both a very low temperature coefficient of the order stated While the processing of the present alloys into resistabove and a resistivity as high as approximately 1000 ance elements may be carried out in a variety of known ohms per 0. m. f. Yet products of that character are ways, the following is one suitable procedure which has highly desirable for a variety of electrical and electronic been employed in processing the examples referred to uses. herein.

It is the principal object of this invention to provide Nickel and chromium in a Weight ratio of approxialloys which can be converted readily into electrical remately 4:1, together with the other essential ingredients slstance elements having both a very low temperature of the composition, are melted together in an electric coefiicient of resistance and an extraordinarily high resisinduction furnace. The melt usually contains minor tivity. Another object is to provide fine electrical reamounts of incidental elements in the nature of impurisistance elements possessing these valuable properties, which are especially suitable for use in precision instruties or degasifying elements, such as C, Ca, Ce, Co, Cu, Fe, Mg, Mn, Pb, Si and/or Zr. The melt is cast into ingots which are heated atabout 2250" F. for 30 to 45 minutes and then are hotrolled'to rod form. The rodsinabath of molten lead, andthen cold drawn through i tungsten may be added in amounts up to about 2% and arsenic or beryllium may be added in amounts up to about .25%--in each case, while retaining the required workability of the alloys as well as their capacity to form electrical resistance elements have the distinctive i) dies to the desired strand size. The cold. drawingis' properties described herein. Table II hereof gives illuseifected in stages .Wlih intermediate steps of annealing at trative examples of alloy compositions embodying this 1750" to 2250 F., pickling, and re-coatingwith lead. invention which contain some of such minor additions, The final strands may bewires as fine as .001 inch, or and shows the resistance properties of heat treated .0253 even smaller, in diameter. i 10 inch wire strands made of the modified alloys.

Table II Strand Heat Time Heat treated strands anneal treat of Example Al V Mo 7 Or Ni Fe Si temp., temp, heat,

F. F treat, Resistivity, '1. 0., SZ/SZ/ 0.

hours Q/G. M. F. (20100 O.)

6 3.76 4.2 2.26 19.09 65.5 5.15 1,750 1,000 32 1, 030 +0.000003 s 2. 97 2.4 2.16 18.5 V 71.08 1.03 1.04 1,750 gg 2 955 0.-o0001s 7 3.04 1.0 4 88 17.8 70. 51 0.74 1.10 1,750 {11% a 962 0.000017 The drawn strands are given a final anneal at 1750. The principles of this invention and preferred ways to 2150 F. in a 12 foot furnace at 42 ft./min. and then 25 of putting it into practice having been described herein cooled rapidly, after which their full resistance properabove, its essential features which we intend to secure ties are developed by heating them in a reducing atmosby letters patent are set forth in the following claims. phere, such as one of hydrogen or cracked ammonia, at We claim: 7 j 900 to 1300.F. for /2 to 100 hours. In general, it has 1. An electrical resistance alloy consisting essentially been found that a higher strand anneal temperature per- 30 of from 2 to 4.5% Al, 1 to 7% V, .1 to Mo and mits the use of a lower heat treating temperature or a 15 to Cr in a Ni base, the total content of Mo shorter time of heat treatment within these ranges. For and Cr not exceeding any given strand anneal'temperature, the higher the heat 2. An electrical resistance alloy consisting essentially treating temperature, the shorter is the time necessary to of from 2 to 4.5 Al, 1 to 7% V, .1 to 10% Mo, 15 i obtain the desired electrical properties. 7 to 20% C1 and 62 to 75% Ni. V j 1 When a composition is described or claimed herein 3. An electrical resistance alloy consisting essentially as consisting essentially of named elements in stated of from 2 to 4.5% Al, 1 to 5% V, l to 10% Mo, 16.5 Q proportions, this expression is intended to mean that the to 20% Cr and 62 to74% Ni. elements so specified are the essential ingredients of the 4. An electrical resistance alloy consisting of approxialloy composition, but it is not intended to exclude the 40 mately 2.5 to 4.5% A1, 2.5 to 4% V, 2 to 10% Mo; presence of minor amounts of various incidental elements 16.5 to 20% Cr and 65 to 70% Ni, with nominal in the nature of usual deoxidizing elements or impurities, amounts of incidental elements from the group consist such as C, Ca, Ce, Co, Cu, Fe, Mg, Mn, Pb, Si and Zr. ing of C, Ca, Ce, C0, Cu, Fe, Mg, Mn, Pb, Si and Zr. Such elements commonly are found in the alloys as a re-J 5. An electrical resistance element comprising a pliable sult of the origin or the manner of-preparationof one strand of an alloy consisting essentially of from 2 to or more of their essential ingredients. Neither is said 4.5% A1, 1 to 7% V, .1 to 10% Mo and 15 to 25% expression intended to exclude the possible addition to Cr in a Ni base, the total content of Mo and Cr not the same composition of minor amounts of elements exceeding 30%, said strand having a resistivity of at which are known to be compatible with electrical resistleast 950 ohms per circular rnil foot and a temperature ance alloys of the nickel-chromium type, to the extent coefficient that does not vary from Zero by not more that such additions do not deprive the products of th than .000020 ohm per ohm per degree centigrade over" valuable resistance properties specified herein. the range of 20 to 100 C.

For example, copper may be added to the present alloys in amounts up to about 5%; iron or cobalt may be References Cited in the file of this P n added to them in amounts up to 5%, or in somewhat UNITED STATES PATENTS larger amounts up to 10% if-added at the expense of nickel; manganese may be added in amounts up to about 5%; silicon may be added in amounts up to about 2.5%;

titanium may be added in amounts up to about 3.5%;

1,803,468 Driver et a1. May 5, 1931 2,005,430 Lohr June 18, 1935 2,460,590 Lohr Feb. 1, 1949 

1. AN ELECTRICAL RESISTANCE ALLOY CONSISTING ESSENTIALLY OF FROM 2 TO 4.5% AL, 1 TO 7% V. .1 TO 10% MO AND 15 TO 25% CR IN A NI BASE, THE TOTAL CONTENT OF MO AND CR NOT EXCEEDING 30%. 